Based in Chicago, Illinois, Telephone and Data Systems, Inc. (TDS) is a diversified telecom service provider offering wireless and wireline services in 35 states. The principal subsidiaries, U.S. Cellular and TDS Telecom, accounted for approximately 82% and 18% of revenue, respectively, in the third quarter of 2007. The company owns 80.6% of U.S. Cellular (USM), the sixth largest wireless operator in the U.S., with over 6 million subscribers as of September 30, 2007. Based in Chicago, USM provides wireless service coverage for TDS in a number of markets (mainly in the Midwest), including Chicago, Milwaukee, Madison, Des Moines, Cedar Rapids, Tulsa, Oklahoma City, Lincoln (NE), Knoxville (TN) and Portland (ME). TDS operates its fixed-line telecom businesses through its wholly-owned subsidiary, TDS Telecom, providing local phone service, long-distance, and Internet access primarily to rural and suburban communities. It operates both as an incumbent local exchange carrier (ILEC), as well as a competitive local exchange carrier (CLEC).